Bubonic plague - Entomologists' glossary - Amateur Entomologists' Society (AES) You are: Home > Insects > Glossary > Definition of Bubonic plague Bubonic plague Bubonic plague is a bacterial disease caused by the bacterium Yersinia pestis. Bubonic plagues kills two thirds of all people who are infected. It is widely believed that bubonic plague was the cause of 'Black Death'; a plague that killed more than 25 million people in the 1300s. Bubonic plague is transmitted through the bite of an infected flea. Commonly these fleas are ectoparasites of rats but, should the host die, they will look for other mammals on which to feed. The bacteria inhabit the flea's gut and when it feeds the bacteria are regurgitated in to the body of the animal the flea is feeding on. Once in the body the bacteria move to the lymph nodes and multiply. A scanning electron micrograph of the bacterium Yersinia pestis. This bacteria casues bubonic plague. Photograph by the United States Federal Government.

Other names for (or types of) Bubonic plague include: Black death Molecular Clues Hint at What Really Caused the Black Death Molecular Clues Hint at What Really Caused the Black Death By Wynne Parry | September 7, 2011 12:25pm ET MORE The Black Death arrived in London in the fall of 1348, and although the worst passed in less than a year, the disease took a catastrophic toll. An emergency cemetery in East Smithfield received more than 200 bodies a day between the following February and April, in addition to bodies buried in other graveyards, according to a report from the time. The disease that killed Londoners buried in East Smithfield and at least one of three Europeans within a few years time is commonly believed to be bubonic plague , a bacterial infection marked by painful, feverish, swollen lymph nodes, called buboes. Plague is still with us in many parts of the world, although now antibiotics can halt its course. [ Pictures of A Killer: A Plague Gallery ] But did this disease really cause the Black Death?

The story behind this near-apocalypse in 14th century Europe is not clear-cut, since what we know about modern plague in many ways does not match with what we know about the Black Death. And if plague isn't responsible for the Black Death, scientists wonder what could've caused the sweeping massacre and whether that killer is still lurking somewhere. Now, a new study using bone and teeth taken from East Smithfield adds to mounting evidence exhumed from Black Death graves and tantalizes skeptics with hints at the true nature of the disease that wiped out more than a third of Europeans 650 years ago. This team of researchers approached the topic with open minds when they began looking for genetic evidence of the killer. "Essentially by looking at the literature on the Black Death there were several candidates for what could have been the cause," said Sharon DeWitte, one of the researchers who is now an assistant professor of anthropology at the University of South Carolina. Their first suspect: Yersinia pestis, the bacterium that causes modern plague, including bubonic plague. The speed of plague In 1894, Alexander Yersin and another scientist separately identified Y. pestis during an epidemic in Hong Kong.

Years later the bacterium was given his name. Yersin also connected his discovery to the pestilence that swept Europe during the Black Death, an association that has stuck. One problem, however, is that compared to the wildfire-like spread of the Black Death, the modern plague moves more leisurely. The modern plague pandemic began in the Yunnan Province of China in the mid-19th century, then spread to Hong Kong and then via ship, to India, where it exacted the heaviest toll, and to San Francisco in 1899, among many other places. The disease that caused the Black Death is believed to have traveled much quicker, arriving in Europe from Asia in 1347, after the Golden Horde, a Mongol Army, catapulted plague-infected bodies into a Genoese settlement near the Black Sea. The disease traveled with the Italian traders and later appeared in Sicily, according to Samuel Cohn, a professor of medieval history at the University of Glasglow and author of "The Black Death Transformed: Disease and Culture in the Early Renaissance Europe" (Bloomsbury USA, 2003).

By about 1352, roughly five years after arriving in Europe, it had not only spread across the continent, the worst of the disease had already run its course. This wave of devastation becomes particularly surprising considering the complicated and time-consuming process by which plague has been thought to spread. You can't catch bubonic plague from another person; instead, the process involves two classic villains: rats and fleas. Once a flea bites a rat infected with plague, the pathogen Y. pestis grows in its gut. After about two weeks, the bacteria block the valve that opens into the flea's stomach. The starving flea then bites its host, by now probably a new, healthy rat or a person, more aggressively in an attempt to feed. All the while, the flea tries to clear out the bacterial obstruction and so regurgitates the pathogen onto the bite wounds, according to Ken Gage, chief of flea-borne disease activity with the U.S. Centers for Disease Control and Prevention. The bulk of cases during the modern plague pandemic are believed to have been spread by rats and their fleas, according to Gage. The last rat-borne plague epidemic in the U.S.

occurred in 1925; wild rodents have since become the primary source for infections. However, rat-associated outbreaks continue to occur in developing countries, according to the CDC. Fast, furious and unfamiliar Not only has the disease slowed down, it also seems to have become more restrained. The Black Death wiped out at least 30 percent of Europe's population at the time. But the peak of the modern pandemic, in India, killed less than 2 percent of the population, DeWitte has calculated from census data. The list of discrepancies goes on: There is evidence the Black Death spread directly between humans — no rats and their fleas involved — and to areas where rats and their fleas didn't even live. In fact, archaeological and documentary evidence indicates rats were scarce during the mid-14th century. What's more, bubonic plague doubters point out, deaths during the Black Death appear to have followed a different seasonal cycle than plague deaths in modern times. Some also point to discrepancies in the symptoms. Alternative theories With the plague's role called into question, other theories have been offered to fill the gap.

"There is a lot of evidence that suggests that Yersinia pestis may not have been the causative agent for the Black Death, and it was likely something else, and something else that is out there right now," said Brian Bossak, an environmental health scientist at Georgia Southern University. He is among those who suspect a hemorrhagic virus — which causes bleeding and fever, like ebola — swept through 14th-century Europe. The high lethality, rapid transmission and periodic resurgences seen in the Black Death are characteristic of a virus, according to Bossak, who frames this as a question in urgent need of resolution. "Who knows if it won't happen again," he said. "It seems like every so often some disease comes out of nowhere." Two other proponents of the virus theory, Susan Scott and Christopher Duncan of the University of Liverpool in the United Kingdom, have pointed to a possible genetic legacy left by a viral Black Death: a mutation, known as CCR5-delta32, found among Europeans, particularly those in the north. This mutation confers resistance against HIV , another virus, but does not prevent plague.

It's possible that by passing over those with this mutation, the Black Death selected for this change in the genetic code, making it more common among Europeans, they argue. To at least some degree, an alternative form of plague, pneumonic plague , offers a solution. While bubonic is the most common form of plague, plague can also infect the lungs, causing high fever, cough, bloody sputum and chills. This infection can spread person-to-person, and without antibiotic treatment it is nearly 100 percent fatal. Outbreaks have occurred in modern times, and it can develop as a result of a bubonic infection. But, it is unclear how much of a role it played in the Black Death — some evidence suggests it is not as contagious as commonly thought. Rats and fleas The Black Death just doesn't appear to have behaved the way the typical, modern rat-associated plague does, according to Gage, the flea expert. Even so, he says he is convinced that bubonic plague was responsible. A group of French researchers found another possible insect carrier for the Black Death: lice. They were able to transmit fatal plague infections from sick rabbits to healthy ones via human body lice that fed on the rabbits.

Substitute humans for bunnies, and this scenario offers a simpler, more cold-climate-friendly explanation than the conventional rat-flea model. But fleas aren't out of the picture yet. Gage and his colleagues have found that many species of flea — including the Oriental rat flea, a widespread and important spreader of plague — can begin transmitting the infection much sooner than thought, before the bacterium blocks off its stomach. This supports the idea that a species of human-inhabiting fleas, whose guts the bacterium can't block well, could have spread the infection from person to person in areas without rats, Gage said. [ 10 Deadly Diseases That Hopped Across Species ] Plague isn't picky about its warm-blooded victims; it can infect almost any mammal, although some, like humans, cats and rats, become severely ill when infected, according to Gage. The lack of records of massive rat die-offs during the Black Death also calls into question the role rats may have played then. CSI: Black Death Plague kills quickly and does not leave marks on the remains that archeologists are digging up centuries later.

But in recent years scientists have begun searching for the molecular clues in the remains of the dead, including DNA left by the killer bacterium. While a number of studies have turned up positive results from graves believed to hold European plague victims, the results haven't always been clear-cut. For instance, a 2004 study of remains in five burial sites, including East Smithfield, was unable to find any evidence of the bacteria. Looking for evidence of the genetic traces of a pathogen within 650-year-old bones is a challenging proposition, according to Hendrik Poinar, an evolutionary geneticist at McMaster University who worked with DeWitte, then at the University of Albany, on the most recent study. After so many years in the ground, the DNA is damaged and present only in tiny fragments, and, what's more, each sample contains only a miniscule amount of the pathogen — the rest belongs to the person and interlopers like soil bacteria, fungi, insects, even animals. "You have to come up with a way to pull out the things of interest," Poinar said.

So, after screening to detect the presence of Yersinia pestis in the 109 samples from the cemetery in East Smithfield, his lab employed a sort of sensitive fishing technique, using tiny segments of DNA that matched up with segments from a ring of DNA, called a plasmid, found in the bacterium. Once they had retrieved this DNA, they assembled the full plasmid and compared it with modern versions of the bug. They found this plasmid matched many of the modern versions. They also sequenced a short section of DNA from the bacterium's nucleus and revealed three small changes unseen in the modern strains. The results prove that a variant of Yersinia pestis infected the victims of the Black Death , the authors write in a recent issue of the journal Proceedings of the National Academy of Sciences. Same bug, different disease? This finding comes about a year after another genetic study, led by Stephanie Haensch of Johannes Gutenberg University in Germany, found evidence of two previously unknown strains of Yersinia pestis in the remains of European victims, and hints at a solution that could allow both sides to be right.

"People have always assumed the two diseases were the same," said Cohn, the medieval historian, referring to modern plague and the Black Death. "Even if it is the same pathogen, the diseases are very different." Bossak, who has questioned the role of plague in the Black Death, agrees. "This new (study) seems to support these earlier claims, and reinforces the notion that what we know of the epidemiology in modern Y. pestis plague may not fit the Black Death, perhaps because these ancient strains of Y. pestis are no longer present (assuming Y. pestis was indeed the causative agent)," he wrote in an email. However, Poinar is more cautious. Although they had hoped to find changes that explained why the pathogen might have become less aggressive over the centuries, none have turned up so far. In fact, it's too early to say the changes detected represent any significant difference between the modern and ancient versions of the bacterium, according to him. "We need the entire genome to say anything about this," Poinar wrote in an email, "and that is for future work." You can follow LiveScience writer Wynne Parry on Twitter @Wynne_Parry .

Follow LiveScience for the latest in science news and discoveries on Twitter @livescience and on Facebook . Editor's Recommendations Bubonic Plague | Science, Health and Physical Education | Video | PBS LearningMedia Background Essay Disease transmission is the process by which contagious diseases are spread from one organism to another. The major pathways through which infectious disease can be spread to an individual include direct or indirect contact; airborne transmission; food, water supply, or blood contamination; and vector-borne transmission. Vector-borne transmission occurs when the disease is not passed directly from person to person, but instead occurs when an infected organism—such as a parasite, insect, or animal—is responsible for carrying the disease and transmitting it to another host. Plague is an example of a bacterial disease that is most commonly transmitted to humans through a vector—here, the bite of an infected flea. In rare cases, humans contract plague through direct contact with an infected animal carcass, or through inhaling droplets expelled when an infected person or animal coughs or sneezes. Malaria is another disease spread through a vector—in this case, the bite of a female Anopheles mosquito infected with a particular parasite. Plague that enters the body through the skin is called bubonic plague.

Far less common forms of plague occur when infection spreads to the lungs or poisons the blood. Bubonic plague is most readily transmitted in urban environments where poor sanitation, overcrowding, and a large population of rodents exist. When rodents become infected, fleas that feed on their blood can spread the disease to other animals they bite. Besides rodents, other animals that carry the bubonic plague bacteria, Yersinia pestis, include lice, dogs, cats, squirrels, and chipmunks. Once inside a human body, plague bacteria travel to the lymph nodes—an important component of the immune system—and begin to multiply. Within two to six days of exposure, plague symptoms develop. These include swollen and tender lymph glands, fever, chills, headache, and general weakness. If bubonic plague is left untreated, its mortality rate can be as high as 90 percent. If patients are diagnosed and treated early with antibiotics, the mortality rate can drop to 15 percent. For centuries, plague devastated populations in Asia, Africa, and Europe. Today, human plague is far less prevalent than other infectious diseases.

A few thousand cases of plague are reported each year worldwide, including an average of 10 to 20 cases in rural areas of the Southwestern United States. In these cases, transmission occurs primarily through flea bites from wild rodent species. Why were San Francisco's health officials so concerned about bubonic plague? Explain why they were right or wrong in the actions they took. How is bubonic plague transmitted? What kinds of environmental conditions increase the transmission of plague to humans? How does an understanding of the transmission of bubonic plague and other diseases help prevent their spread? Today, plague still threatens as a health problem in communities in New Mexico. Can you think of reasons why this might be the case? Plague Plague By Jerrod R Anderson Disease etiology Plague is an infectious disease of animals and humans caused by a bacterium named Yersinia pestis. (1) There are three different types of plague, Bubonic, the most commonly plague found in humans, Septicemic and Pneumonic. (2) Disease transmission The disease is transmitted via animals or insect vectors and are injected into humans or animals via a flea bite, or a bite from infected animals or rodents.

Another form why that the organism can be transmitted is through the air, or aerosol transmission, this can happen with Pneumonic plague. In this case, the micro organisms are released by an infected host, and inhaled by a new host. (4) Reservoirs The most common vector is the rat flea; however there are thirty different flea species that have been identified as carriers. Other carriers include cats and dogs, chipmunks, deer mice, rabbits, and sheep. (4) Mostly the reservoirs are various rodents, insects and other animals, which then pass the disease to humans. Specific microbial characteristics Yersinia pestis is a Gram-negative bacillus bacterium that belongs to the Enterobacteriaceae family. This particular bacterium is a facultative anaerobe, meaning that it prefers to be in the presence of oxygen, however is capable of surviving with out oxygen. The optimal temperature for this particular bacterium is 28 degrees Celsius. Since this particular bacteriumï¿½s natural reservoirs are in rodents and insects, it is a zoonose, which means that it is a disease that is passed from animals to humans through direct or indirect contact.

(3) Specific tests for identification One of the first steps when attempting to identify a bacterium as Yersinia pestis is to perform a gram stain to ensure that you in fact have a gram negative bacillus organism. The specimen that is used for this particular test should be collected from an appropriate site for isolating the bacterium, as in the bubo from a patient that has bubonic plague. It is also suggested to do blood smears on patients, especially patients who are suspected to have septicemic plague, however the blood smear for a patient with bubonic plague would be negative. The blood smear should be taken in 20 to 30 minute increments because bacterium may be intermittently released by infected lymph nodes. If the patient is believed to be infected with pneumonic plague, then a sputum/throat smear should be used. The problem with this particular smear is that there will be additional normal flora that are present in the smear, so it is necessary to stain the microbes and use a more specific fluorescent-antibody (FA) test. (1) Yersinia pestis can be grown on general laboratory media for instance agar, and can be isolated by streaking the plate for isolation.

If there is a chance that there might be multiple microbes, then the samples can be purified by passing the organism through laboratory mice, which will yield pure Yersinia pestis. (1) The plague bacilli express a unique diagnostic envelope glycoprotein called the Fraction 1 (F1) antigen or capsular antigen. This particular antigen is the primary target used for plague diagnostic FA and antibody tests. Biochemical profiles, which should only be used as a supplemental diagnostic tool, are not as reliable because plague bacilli are relatively inactive by standard enteric biochemical reactions. (1) One important note about identification is that if a person has already been on antibiotics for more than 4 days, then it is necessary to incubate a bacterium culture for 5 days to allow the bacterium to recover. (1) A final tool for identification, if all of the other tests come back negative, is to perform serological tests. In this case, one serum sample should be taken early in the illness, and the another sample 1-4 months after antibiotics use has deceased.

(1) Signs and Symptoms Some of the common general symptoms include fever, chills, sore throat, body ache, abdominal pain, nausea, and stiff neck, shortness of breath, confusion and seizures. Bleeding into the skin can cause the skin to turn black, which is how the term black plague arose, which is a common nickname. (4) Another very distinguishable symptom of plague is a bubo, which is a painful, swollen, and hot to the touch lymph node. (1) Historical information Plague has an extensive history that dates back along time ago, and can be read about in the bible. However there are three main occurrence of a plague pandemic, which is an unexpected rise in the occurrence of the disease over a large area. The first pandemic was named the Plague of Justinian. This particular pandemic happened in two parts, A.D. 541-542 and A.D. 588. It was the first heavily documented outbreak of the plague and was the result of a massive amount of rats and fleas in the granaries of Constantinople. The first outbreak killed about 40% of the total population with a peak death rate of about 10,000 people per day.

The second outbreak spread through the Mediterranean and into France. The overall outcome of the Plague of Justinian was that it dropped the European population to about 50% and killed a total of as many as 100 million people. (3) The second pandemic originated in Central Asia and was named the ï¿½black death. This particular pandemic was between 1347 and 1351; not only hitting Central Asia, but Europe and Africa as well. The total damage of this pandemic was close to 100 million with Europe losing about 1/3 of its population and China losing about ï¿½ of its population. (3) The third pandemic began in China in 1855 and spread to all inhabited continents. This particular plague differed from the first two in the fact that it was not only bubonic plague, but it was also pneumonic plague as well. The third pandemic lasted for over a century when it hit Hawaii in 1959. This pandemic is what eventually led to the modern treatment methods of plague.

(3) Virulence factors One of the most interesting factors about the microorganism that causes plague is that it does not affect the host vector, or the flea, however it does have a unique virulence factor which inhibits the response of the immune system of humans and rodents. The virulence factors that help Yersinia pestis survive come from the fact that it is a gram negative bacterium. This means that the bacterium has an endotoxin, which is part of the outer membrane of the bacterium cell wall. The activity of endotoxin is associated with the lippopolysaccharide (LPS), with toxicity being associated with the lipid component and immunogenicity being associated with the polysaccharide portion component. The LPS is the bacterium defense against complement mediated lysis or the actions of the lysosomes of the infected individual, which gives the bacterium the chance of survival. (5) Another factor that contributes to this bacterium is the presence of plasmids, which replicate separately from chromosomal DNA. These plasmids are what give the bacterium the ability to develop resistance to antibiotics and the ability to survive in fleas.

(6) Control/Treatment One of the most important control mechanisms available for controlling plague would be to control the vectors responsible for the bacterium. It is necessary to control the rat population so that the amounts of rat fleas are limited. If there is a large population of rats, then there is a greater chance of them transmitting the plague to humans. However if the rat population, or other rodent populations for that matter, are kept within a reasonable range, then the chances of plague are greatly reduced. The treatment of plague starts by isolating the patients so that the bacterium does not spread. They are then started on antibiotic treatment. These antibiotics include, but are not limited to Streptomycin, Tetracycline, Chloramphenicol, and other antibiotic. (3) There are also supportive therapies that may be required, including respiratory support, intravenous fluids and oxygen, depending on how severe and complicated the case is. (2) Prevention/Vaccines Although there was a vaccine for plague, it is no longer used or not as commonly used. The previous vaccine only worked against the bubonic plague. There is currently a new vaccine under development.

The most appropriate way to prevent contraction of plague is to ensure you do not come in contact with wild animals, and if you do, be sure to watch for the signs of plague so that you can catch it early. (4) It is also necessary to isolate a person who may have plague, to ensure that the bacterium is not allowed to spread, which in turn could very well cause another pandemic. Local cases/outbreaks There are several distinct areas throughout the southwest part of the United States that are more susceptible to plague outbreaks. Below is a map of the local and worldwide distribution of plague from 1970 to 1998. The last rat-borne epidemic of plague in the United States was in Los Angeles in 1924-25. Since then, all human plague cases in the United States have been sporadic and are usually caused by wild rodents or their fleas. Although the human cases of plague are sporadic, it is believed that the plague bacterium is believed to circulate within rodent populations without causing excessive mortality.

(1) On average, during the 1980ï¿½s there were only about 18 cases per year of plague in the United States, with most of the cases showing up in people who were under the age of 20. During this time period, about 1 in 7 people who were infected with plague died. (1) (1) Global cases/outbreaks As the map below shows, there are several regions outside the United States that have plague cases, however there are also many regions that have not had a single case of plague. A couple of example of areas that have not had plague outbreaks, at least in the recent past, are Australia and Europe, which had the last reported case of plague after WWII. (1) According to the World Health Organization there have been several outbreaks of plague in the past decade. In 2006, there was a reported outbreak of plague in Democratic Republic of the Congo, at which point there were 626 suspected cases and 42 deaths. However during this time period, it was suspected that the number of cases was incorrect due to the low fatality ratio.

In 2005, pneumonic plague broke out in the Democratic Republic of the Congo, more specifically in the Zobia, Bas-Uï¿½lï¿½ district, Oriental province. During this outbreak, there were 130 suspected cases and a total of 57 deaths. In 2003, there were 10 cases of plague in Algeria, 8 cases of bubonic plague and 2 cases of septicemic plague. This small outbreak only resulted in one death. In 2002 there were 16 cases of pneumonic plague in India that resulted in 4 deaths. The final report was in 2001 where there were 23 cases of plague that resulted in 3 deaths in Zambia. On a more non specific note, the WHO found that there were 38,310 cases of plague resulting in 2845 deaths in 25 countries from 1989 to 2003. (7) Male Xenopsylla cheopis (oriental rat flea) engorged with blood. This flea is the primary vector of plague in most large plague epidemics in Asia, Africa, and South America.

Both male and female fleas can transmit the infection. (1) References (1) Center for Disease Control and Prevention. ï¿½CDC Plague Home Page.ï¿½ Updated June 25, 2009. URL: . Accessed February 22, 2010. (2) Mayo Clinic. ï¿½Plague.ï¿½ Updated August 30, 2008. URL: . Accessed February 22, 2010. (3) University of South Carolina School of Medicine. ï¿½Microbiology and Immunology On-line.ï¿½ Updated May 05, 2009. URL: . Accessed March 3, 2010. (4) Medicine Net. ï¿½Plague.ï¿½ Updated January 16, 2008. URL: . Accessed February 22, 2010. (5) Todar, Kenneth PhD. ï¿½Todarï¿½s Online Textbook of Bacteriology.ï¿½ URL: . Accessed March 3, 2010.

(6) US Department of Energy Research. ï¿½Tracking down virulence in plague.ï¿½ Updated March 2, 2002. URL: . Accessed on February 23, 2010. (7) World Health Organization. ï¿½Plague.ï¿½ Updated Febuary 2005. URL: . Accessed on March 3, 2010. Plague | Public Health and Medical Entomology | Purdue | Biology | Entomology | Insects | Ticks | Diseases | Monitoring | Control | Hot Topics | Agriculture | Extension Murine Typhus Plague Plague has surfaced several times in major, world-wide epidemics, one of the most important of which was the so-called "black death" that devastated Europe in the 14th century, when an estimated 25,000,000 people died. Historically, plague outbreaks have started slowly with transmission of the disease agent, a bacterium, via the bite of infected rodent fleas, primarily the Oriental rat flea, but then developed into rapidly growing epidemics involving human-to-human transmission (see below).

The initial infection following feeding by an infected flea is marked by painful, swollen lymph nodes, initially in the groin region. This form of plague is known as "bubonic plague," which, if untreated, can develop into a form of plague known as "septicemic plague." In septicemic plague, bacteria invade the blood and infect major body organs. In addition to damaging organs and causing internal hemorrhage, septicemic plague can develop rapidly into a highly infectious disease condition known as "pneumonic plague." In pneumonic plague, bacteria infect a patient's lungs and may be spread via coughing. If untreated, fatality rates of septicemic and pneumonic plague are as high as 50-90%, and they approach 15% even when treated promptly with antibiotics. Today, plague exists as a disease of wild rodents in most of the arid regions of the world, including the western U. S. and southwestern Canada. Every year, a small number of people (approximately 10-15 per year) in the southwestern U.S. become infected with plague, typically after venturing into or living in or adjacent to areas in which they are bitten by infected fleas that are parasites of wild rodents.

One of the most important vectors is a flea species with the scientific name Oropsylla montana. This flea is a parasite of the rock squirrel, Citellus variegatus, which is a common reservoir animal, from which fleas acquire plague bacteria when they take a blood meal. Causative agent A bacterium with the scientific name Yersinia pestis (Pasteurella pestis in older literature). It is a highly infectious, invasive, and dangerous bacterium. Geographical distribution of cases World wide, 1,000-3,000 cases per year, primarily in arid regions of Asia, Africa, and the Americas. In the U.S. from 1971-1995, 1-40 cases per year (average of 13), nearly all in southwestern states. Symptoms of infection Bubonic plague: high fever, chills, and painful, swollen lymph nodes. Septicemic plague: rapid rise of high fever, abdominal pain, and internal hemorrhage. Pneumonic plague: high fever, breathing difficulties, coughing, and bloody sputum. Reservoir hosts of Yersinia pestis in the U.S.

Numerous species of wild rodents and several species of rodents that live in or near humans, including the rock squirrel and certain species of ground squirrels and chipmunks. NOTE: Prairie dogs typically die too quickly of the infection to be considered reservoir hosts. Vectors of Yersinia pestis in the U.S. In rural regions: numerous species of fleas that are parasites of wild rodents. In urban areas: the primary vector is the Oriental rat flea Xenopsylla cheopis. Modes of Transmission Bubonic plague: via the bite of infected fleas. Pneumonic plague: human-to-human via air-borne droplets associated with coughing. NOTE: Cats also can develop pneumonic plague, and cat to human transmission has been reported. NOTE: Unlike cats, dogs do not appear to develop pneumonic plague. Diagnosis of infection Bubonic plague: swollen and painful lymph nodes, severe headache, fever, and shaking chills. Pneumonic plague: pneumonia-like symptoms such as coughs, bloody sputum, chills, and high fever. Septicemic plague: difficult to diagnose (except by blood analysis) and progresses very rapidly.

Treatment of infection Physician prescribed antibiotics administered within hours of the onset of symptoms of bubonic plague. Antibiotic treatment of pneumonic and septicemic plague often is unsuccessful. Prevention of infection There is no vaccine available in the U.S. Restrict human access into areas in which plague transmission is occurring in wild rodents. Use an insect repellent such as DEET when entering plague-infested areas. Be aware of the possibility of pneumonic plague, especially in cats that exhibit signs of pneumonia. Control of vectors Avoid landscaping that encourages wild rodents in and adjacent to residential and recreational areas. NOTE: Large boulders used in landscaping often encourage nesting by the rock squirrel. Monitor pets that venture into wild rodent habitat for the presence of rodent fleas. Consult a veterinarian regarding flea control on pets. NOTE: The cat flea is not a vector of plague. WWW Bubonic plague found in Arizona after fleas infect prairie dog burrow — RT America Public health officials noticed a prairie dog burrow where animals appeared to be dying off and saw at least one dead prairie dog, Randy Philips, division manager with the Coconino County Public Health Services District, told the Arizona Daily Sun.

"It looked like something that could be associated with death due to plague," Philips said. The first round of testing took place over a limited area of Picture Canyon, just north of the Wildcat Wastewater Treatment Plant in east Flagstaff. On Thursday, they went back to sample more flea colonies over a much broader area, Phillips said. Those results are due back later this week. — Breaking3zero U.S (@Breaking3zeroUS) April 6, 2015 On Saturday, officials began clearing and disinfecting burrows in the area with insecticides, in an attempt to prevent any possible outbreak of the plague. Arizona has experienced 64 cases of the disease since 1950 , when the first known human case of plague occurred. Since then, there has been an average of one to two human cases per year, according to the Arizona Department of Health Services (ADHS). Only one person has died from the disease since 2000, and two others survived after contracting it. "Plague activity in nature has been known to wax and wane over time, and this is influenced largely by climate conditions and rodent and flea populations," ADHS says on its website.

Three states in the American southwest ‒ Arizona, Colorado and New Mexico ‒ are responsible for 80 percent of human cases of the plague, Dave Engelthaler, programming director with pathogen research nonprofit TGen North, told the Arizona Daily Sun. The last time the plague was found in Arizona was September 2014, when fleas in Doney Park tested positive for the disease, the Arizona Republic reported at the time. Don't feed the squirrels. Don't get the plague. #grandcanyon #arizona #nationalparks by floydfarley pic.twitter.com/ceojktpa2N — NationalParks Photos (@NatlParksPhotos) February 15, 2015 Researchers believe it may be because the Southwest’s climate, topography and rodent populations are similar to the high desert grasslands of central Asia where plague first evolved, David Wagner, a professor at Northern Arizona University’s Microbial Genetics and Genomics Center, told the Arizona Daily Sun. “It found a similar place to make a new home,” Wagner said.

READ MORE: NYC rats carry Bubonic plague-transmitting fleas - study Fleas on rabbits and other small rodents ‒ including prairie dogs, ground squirrels, rats and mice ‒ carry the Yersinia pestis bacteria that causes the bubonic plague. Prairie dogs are especially vulnerable to the disease due to their social nature, and outbreaks can quickly wipe out 90 percent of a local prairie dog population. "If you normally see prairie dogs then next day they're gone, there is a good chance plague is coming," Engelthaler said. Humans usually contract the plague after being bitten by a rodent flea that is carrying the bubonic plague bacterium or by handling an animal infected with plague, according to the US Centers for Disease Control and Prevention (CDC). To prevent the disease from spreading to humans, ADHS warns visitors and residents not to allow pets to roam freely, as well as treating them with flea-prevention medications; to avoid contact with sick or dead animals and to stay away from rodent burrows; to wear insect repellents to keep fleas away when hiking or working in areas where plague might be active; and to wear rubber gloves when skinning and cleaning game animals.

— 12 News (@12News) April 2, 2015 Today, modern antibiotics are effective in treating plague, the CDC says. However, the disease can cause serious illness or death without prompt treatment. Plague symptoms include fever; headache; pain or swelling in the groin, armpit or neck area; weakness; and, occasionally, nausea. Symptoms usually appear within two to six days after exposure. Rats are exonerated as reservoir hosts for the Black Death - BugBitten BugBitten The black rat, Rattus rattus. Sourse: wiki commons Doctor Schnabel [Dr. Beak], a plague doctor in seventeenth-century Rome. Source: wiki commons The grim reaper, a symbol of the Black Death: wiki commons Most British school children are familiar with the story of the Black Death and subsequent plague epidemics that decimated the population of Europe in the Middle Ages. It now seems that the villain of the plot, the black rat, may have been wrongly accused of acting as a European reservoir for the plague bacteria and initiating sporadic disease outbreaks for 400 years. Contrary to many people’s understanding, the plague is not a thing of the past.

Although it disappeared from Europe in the early 1900s it still persists in many pockets around the world (see map), as witnessed by the current outbreak in Madagascar . Analysis of DNA and immunoprotein samples from the remains of medieval plague victims has confirmed that the Black Death and subsequent plague epidemics were caused by the same bacterium, Yersinia pestis , as modern day outbreaks. Shortly after Alexandre Yersin’s discovery, in the l890s, of the bacillus that caused the European plague pandemics, the accepted medical understanding was that plague was transmitted to humans from fleas infesting black rats; infected fleas thus acting as vectors. When rats began dying of the disease in large numbers infected fleas bit humans as an alternative host and thus infected them. However the role of the black rat has been challenged by several investigators. For example, Anne Karin Hufthammer made a case against the involvement of black rats in plague epidemics in Scandinavia. She based her challenge on archeological information from bone assemblages that showed that black rats were very rare in medieval Norway, despite regular outbreaks of the plague.

Indeed it is likely that the colder climatic conditions across Europe during this period would not have been conducive to the survival of populations of the black rat nor the Oriental rat flea, Xenopsylla cheopsis in most of Europe. The now common brown rat had not arrived in Europe at this time. One of the places where the plague bacterium persists is in the Central Asian Deserts, where the great gerbil, Rhombomys opimus, is the primary host. Gerbils are social animals, living in burrows infested with several parasitic arthropods, including the fleas that act as vectors for the bacterium. Gerbil populations fluctuate and the sylvatic plague bacterium will spread in the population when it exceeds an upper threshold level. Work published in 2007 by Nils Christian Stenseth and colleagues, who were studying the gerbil populations in Kazakhstan, suggested a co-dependency exists between climatic conditions, vegetation cover, synchronised increase in gerbil densities and plague transmission. Warm, moist conditions promote vegetation growth in these arid areas, giving rise to large gerbil populations and large plague epizootics.

As gerbil populations crash, flea populations rise, the plague bacteria spread and infected fleas spill-over onto domestic animals and humans. The latest study from this group has just been published . Here they asked whether climatic fluctuations were also responsible for the waves of plague pandemics that swept Europe after the initial Black Death of 1347-1353. There are, of course, no reliable climatic records from the 13th / 14th century and so Stenseth and his colleagues used tree-ring based data as a climate proxy when looking for a relationship between climate fluctuations and plague outbreaks in medieval Europe. They used historical records of 7,711 plague outbreaks that occurred after the Black Death and data from the analysis of 15 tree-ring based climate proxies taken across Europe and Asia. Unlike modern Asian outbreaks, no association could be found between plague outbreaks and climatic conditions. Furthermore, there was little evidence that there was a local wildlife reservoir of Y. pestis that could have initiated new outbreaks.

To determine this they selected outbreaks that occurred within 500 km of the location where one of the tree-ring samples had been taken and where, within a radius of 1000 km, there had been no previous plague outbreak in the past 2 years that could have been the source of the new outbreak. This analysis suggested that most outbreaks could be attributed to previous outbreaks nearby, as only 24 episodes remained that could only have been initiated by reservoirs of bacteria in the local rodent populations. In addition, 8 of these were historically documented to have been introduced with shipping from plague infested areas. These findings caused then to turn their attention to the possibility that each new wave of disease had a maritime origin. Using the same criteria to select locations, they were able to detect 61 potential maritime introductions that occurred between 1346 and 1856 in 17 harbours around the Mediterranean and the Black Sea coasts. These sea routes linked Europe with the overland routes to Asia. Historical reports were used to identify 16 potential introductions from Asia. Periods of climatic fluctuations were identified from tree ring analysis at sites on these ancient trade routes to Central Asia.

Here populations of long tailed ground squirrels and Altai marmots are the rodent reservoir of plague. Map of the spread of the Black Death: Source, #blackdeathanch They found that a period of approximately 15 years consistently occurred between a climatic fluctuation in the Karakorum mountain range in northern Pakistan and a plague reintroduction in Europe. This suggest a scenario whereby; 1-2 years after a climatic fluctuation, the rodent populations crashed and infected fleas sought alternative hosts. A period of 10-12 years followed when, they hypothesised, the disease travelled West via caravan routes to the sea (the ancient Silk Road). It took a further 2-3 years to spread into Europe via maritime trade routes. Evidence for the spread via the ancient caravan routes requires further investigation but camels are easily infected with plague from the bites of fleas and the bacillus could also have travelled in infected traders, other animals or fleas in their cargo. It would appear that we may need to rewrite the history books and place the blame for these ancient scourges that changed the face of Europe upon the trade in exotic goods rather than the humble rat.

Transmission | Plague | CDC Plague ecology in the United States. A downloadable version [PDF - 1 page] is also available. The bacteria that cause plague, Yersinia pestis, maintain their existence in a cycle involving rodents and their fleas. In urban areas or places with dense rat infestations, the plague bacteria can cycle between rats and their fleas. The last urban outbreak of rat-associated plague in the United States occurred in Los Angeles in 1924-1925. Since that time, plague has occurred in rural and semi-rural areas of the western United States, primarily in semi-arid upland forests and grasslands where many types of rodent species can be involved. Many types of animals, such as rock squirrels, wood rats, ground squirrels, prairie dogs, chipmunks, mice, voles, and rabbits can be affected by plague. Wild carnivores can become infected by eating other infected animals. Scientists think that plague bacteria circulate at low rates within populations of certain rodents without causing excessive rodent die-off. These infected animals and their fleas serve as long-term reservoirs for the bacteria. This is called the enzootic cycle.

Occasionally, other species become infected, causing an outbreak among animals, called an epizootic. Humans are usually more at risk during, or shortly after, a plague epizootic. Scientific studies have suggested that epizootics in the southwestern United States are more likely during cooler summers that follow wet winters. Epizootics are most likely in areas with multiple types of rodents living in high densities and in diverse habitats. Transmission The plague bacteria can be transmitted to humans in the following ways: Flea bites. Plague bacteria are most often transmitted by the bite of an infected flea. During plague epizootics, many rodents die, causing hungry fleas to seek other sources of blood. People and animals that visit places where rodents have recently died from plague are at risk of being infected from flea bites. Dogs and cats may also bring plague-infected fleas into the home. Flea bite exposure may result in primary bubonic plague or septicemic plague. Contact with contaminated fluid or tissue. Humans can become infected when handling tissue or body fluids of a plague-infected animal. For example, a hunter skinning a rabbit or other infected animal without using proper precautions could become infected with plague bacteria.

This form of exposure most commonly results in bubonic plague or septicemic plague . Infectious droplets. When a person has plague pneumonia, they may cough droplets containing the plague bacteria into air. If these bacteria-containing droplets are breathed in by another person they can cause pneumonic plague . Typically this requires direct and close contact with the person with pneumonic plague. Transmission of these droplets is the only way that plague can spread between people. This type of spread has not been documented in the United States since 1924, but still occurs with some frequency in developing countries. Cats are particularly susceptible to plague, and can be infected by eating infected rodents. Sick cats pose a risk of transmitting infectious plague droplets to their owners or to veterinarians. Several cases of human plague have occurred in the United States in recent decades as a result of contact with infected cats. File Formats Help:

Question: Which insect is responsible for transmitting the bubonic plague?
Answer: Flea